This invention is directed toward a method for accelerating the dehydration of aqueous polymeric dispersions and improving the bonding of the solids contained therein by the addition of fly ash. Generally, aqueous polymeric compositions of the invention are latexes prepared by adding fly ash to the aqueous dispersion of polymer particles such that the dehydration or set time of the latex composition is significantly reduced as compared to a latex composition prepared in the absence of fly ash. In addition to the decrease in dehydration time, the polymeric compositions have enhanced physical properties due to the reactive nature of the fly ash which improves the bonding of the solids.
A latex composition is generally defined as a stable dispersion of a polymeric substance in an essentially aqueous medium. Latex compositions are employed in a variety of uses which require that the aqueous phase be removed such that the polymeric particles and other solids present in the aqueous phase can be distributed onto a substrate and form a film. The formation of this film generally requires a substantial amount of energy in order to remove the aqueous phase portion of the latex composition. Methods of reducing the amount of energy needed to remove the aqueous phase are, therefore, desirable. It is further desirable to develop means to improve the physical interaction of the various solids present in the latex composition such that films having increased physical properties can be formed.
Fly ash is a waste by-product of large scale coal fueled power generation plants and; therefore, it is desirable to find uses for fly ash from an ecological standpoint. Attempts to utilize fly ash have been made as disclosed in U.S. Pat. No. 4,088,804 where fly ash is added to cement compositions to react with the calcium hydroxide produced during the curing of the cement. Additionally, U.S. Pat. No. 4,425,440 discloses that fly ash can be employed to form a thermally insulating material and a flame retardant thermal insulation and U.S. Pat. No. 4,229,329 discloses the use of fly ash to prepare a fire retardant coating composition useful as paints or mastics.
The subject method for employing fly ash in latex compositions greatly reduces the energy requirements required for removing the latex solids from the aqueous phase and additionally provides enhancement of the physical properties of the latex film. The use of fly ash in the preparation of latex films therefore is of great ecological value in that it reduces the energy required to prepare a latex film and takes advantage of a by-product from the production of energy.